slmkfs/mkfs.c

// This is NEW CODE by Zak to replace the old xv6 mkfs program.
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

// These are the similar to in the old mkfs program but will be slowly
// replaced. The stat structure needs to be #defined away (or replaced
// with some other name) because "stat" will likely be defined already
// on whatever operating system mkfs is running on.
#define stat kernel_stat
#include "slkern/types.h"
#include "slkern/fs.h"
#include "slkern/stat.h"
#include "slkern/param.h"

#include "fsformat.h"

typedef struct mkfs_job mkfs_job_t;
struct mkfs_job {
  int device;
  int rootinodenumber;
  
  int fsversion;        // Filesystem version, 0 for compatibility 1 is standard
  int blocksize;        // The block size, currently 4096 is the standard
  int totalblocks;      // Total number of blocks in the filesystem we're making
  int inodecount;       // Number of inodes (i.e. maximum number of files/dirs)
  
  int specialblocks;    // Should be 2, boot block and superblock at beginning
  int logblocks;        // Size of the log area in blocks
  int inodeblocks;      // Size of the inode area in blocks
  int bitmapblocks;     // Size of the used/free bitmap in blocks
  
  int metablocks;       // Total number of special/log/inode/bitmap blocks
  int datablocks;       // Total number of data blocks (not including metadata)
  
  int block_nextfree;   // Next free block to allocate
  int inode_nextfree;   // Next free inode to allocate
  
  int inodesize;
  int inodesperblock;
  
  int inoderefsize;     // Set to 2 for small fs or v1, set 4 for normal
  int filenamesize;     // Set to 14 bytes for v0 or flexible for v1+
  int directblocks;     // Number of simple "direct" blocks of file data
  int indirectblocks;   // Number of blocks-of-blocks for more file data
  
  // The superblock is configured using MKFS_DISKORDER* macros for byte order.
  fsformat_superblock_t* superblock;
};

// The mkfs_io_* functions will need to be modified if mkfs is used inside the
// kernel or in some other circumstances than running on Linux. Currently the
// same options are used internally as for the old filesystem code.

int mkfs_io_opendevice(mkfs_job_t* job, char* filename) {
  return open(filename, O_CREAT | O_RDWR | O_TRUNC, 0666);
}

int mkfs_io_closedevice(mkfs_job_t* job) {
  close(job->device);
  return 0;
}

// This is only used internally by the other IO functions and need not exist
// on other device IO implementations.
int mkfs_io_seekblock(mkfs_job_t* job, int blocknumber) {
  int offset = job->blocksize * blocknumber;
  if (lseek(job->device, offset, 0) == offset) {
    return 0; // Good, seek'ed to write offset
  }
  return -1; // Bad, seek failed
}

int mkfs_io_readblock(mkfs_job_t* job, int blocknumber, void* buffer) {
  if (mkfs_io_seekblock(job, blocknumber) != 0) {
    return -1;
  } else if (read(job->device, buffer, job->blocksize) != job->blocksize) {
    return -1;
  }
  return 0;
}

int mkfs_io_writeblock(mkfs_job_t* job, int blocknumber, void* buffer) {
  if (mkfs_io_seekblock(job, blocknumber) != 0) {
    return -1;
  } else if (write(job->device, buffer, job->blocksize) != job->blocksize) {
    return -1;
  }
  return 0;
}

// These should be changed if mkfs is ever ported to a big-endian system, but
// otherwise can simply fall through:
unsigned short mkfs_diskorder16(unsigned short x) {
  return x;
}

unsigned int mkfs_diskorder32(unsigned int x) {
  return x;
}

unsigned long long mkfs_diskorder64(unsigned long long x) {
  return x;
}

#define MKFS_DISKORDER16(x)   mkfs_diskorder16(x)
#define MKFS_DISKORDER32(x)   mkfs_diskorder32(x)
#define MKFS_DISKORDER64(x)   mkfs_diskorder64(x)

#define MKFS_INODEBLOCK(job, inodenumber) \
  (((inodenumber) / job->inodesperblock) + MKFS_DISKORDER32(job->superblock->firstinodeblock))
#define MKFS_INODEINDEX(job, inodenumber) \
  ((inodenumber) % job->inodesperblock)

mkfs_job_t* mkfs_job_alloc(int fsversion, char* filename, int blocksize, int totalblocks, int logblocks, int inodecount, int directblocks, int indirectblocks, int inoderefsize, int filenamesize) {
  if (fsversion == 0) {
    // Check that inode/filename sizes match v0 or else fail.
    if (inoderefsize != 2 || filenamesize != 14) {
      return NULL;
    }
  } else {
    // Filesystems >= v1 support 2-byte (16-bit) or 4-byte (32-bit) refs
    if (inoderefsize != 2 && inoderefsize != 4) {
      return NULL;
    }
  }
  
  mkfs_job_t* result = malloc(sizeof(mkfs_job_t));
  if (result) {
    result->fsversion = fsversion;
    result->blocksize = blocksize;
    result->totalblocks = totalblocks;
    
    result->device = mkfs_io_opendevice(result, filename);
    if (result->device < 0) {
      free(result);
      return NULL;
    }
    
    result->inoderefsize = inoderefsize;
    result->filenamesize = filenamesize;
    result->directblocks = directblocks;
    result->indirectblocks = indirectblocks;
    
    result->inodesize = 12 + ((directblocks+indirectblocks) * 4);
    result->inodesperblock = blocksize / result->inodesize;
    
    result->specialblocks = 2;
    result->logblocks = logblocks;
    result->inodeblocks = (inodecount / result->inodesperblock) + 1; // TODO: Stabilise inode structure and it's size
    result->bitmapblocks = (totalblocks / (blocksize*8)) + 1;
    
    result->metablocks = result->specialblocks + result->logblocks + result->inodeblocks + result->bitmapblocks;
    result->datablocks = result->totalblocks - result->metablocks;
    
    result->inodecount = inodecount;
    
    result->block_nextfree = result->metablocks;
    result->inode_nextfree = 1;
    
    result->superblock = malloc(sizeof(fsformat_superblock_t));
    result->superblock->magic = MKFS_DISKORDER32(fsversion == 0 ? FSFORMAT_MAGIC_OLD : FSFORMAT_MAGIC_NEW);
    result->superblock->totalblocks = MKFS_DISKORDER32(result->totalblocks);
    result->superblock->datablocks = MKFS_DISKORDER32(result->datablocks);
    result->superblock->inodelimit = MKFS_DISKORDER32(result->inodecount);
    result->superblock->logblocks = MKFS_DISKORDER32(result->logblocks);
    result->superblock->firstlogblock = MKFS_DISKORDER32(result->specialblocks);
    result->superblock->firstinodeblock = MKFS_DISKORDER32(result->specialblocks + result->logblocks);
    result->superblock->firstbitmapblock = MKFS_DISKORDER32(result->specialblocks + result->logblocks + result->inodeblocks);
    
    // Set the extended flags only for version 1.
    if (fsversion >= 1) {
      result->superblock->extd_versionflags = MKFS_DISKORDER32(fsversion);
      result->superblock->extd_inodestructsize = MKFS_DISKORDER32((int) sizeof(fsformat_inode_t));
      result->superblock->extd_blocksize = MKFS_DISKORDER32(blocksize);
      result->superblock->extd_superblocksize = MKFS_DISKORDER32((int) sizeof(fsformat_superblock_t));
      result->superblock->extd_inoderefsize = MKFS_DISKORDER32(inoderefsize);
      result->superblock->extd_filenamesize = MKFS_DISKORDER32(filenamesize);
      result->superblock->extd_directblocks = MKFS_DISKORDER32(directblocks);
      result->superblock->extd_indirectblocks = MKFS_DISKORDER32(indirectblocks);
    }
  }
  return result;
}

unsigned char* mkfs_allocblockbuffer(mkfs_job_t* job) {
  return calloc(1, job->blocksize);
}

void mkfs_freeblockbuffer(mkfs_job_t* job, unsigned char* buffer) {
  free(buffer);
}

// Marks all blocks up to #blocksused as in-use
void mkfs_markused(mkfs_job_t* job, int blocksused) {
  unsigned char* buffer = mkfs_allocblockbuffer(job);
  
  printf("mkfs_markused(job, %d)\n", blocksused);
  
  if (blocksused >= (job->blocksize * 8)) {
    fprintf(stderr, "mkfs_markused: This function only works for creating small disks that won't use more than 1 page of the free/used bitmap\n");
    exit(-1);
  }
  
  // Should already be cleared by mkfs_allocblockbuffer: memset(buf, 0, job->blocksize)
  
  for (int blocknum = 0; blocknum < blocksused; blocknum++) {
    int idx = blocknum / 8;
    int mask = 1 << (blocknum % 8);
    buffer[idx] |= mask;
  }
  
  // NOTE: The old code did not seem to consistently use disk endian functions.
  printf("mkfs_markused: Writing bitmap block %d\n", MKFS_DISKORDER32(job->superblock->firstbitmapblock));
  
  mkfs_io_writeblock(job, MKFS_DISKORDER32(job->superblock->firstbitmapblock), buffer);
  
  mkfs_freeblockbuffer(job, buffer);
}

void mkfs_readinode(mkfs_job_t* job, unsigned int inodenumber, fsformat_inode_t* inode) {
  unsigned int blocknumber = MKFS_INODEBLOCK(job, inodenumber);
  unsigned int inodeindex = MKFS_INODEINDEX(job, inodenumber);
  void* buffer = mkfs_allocblockbuffer(job);
  fsformat_inode_t* inodebuffer = (fsformat_inode_t*) buffer;
  fsformat_inode_t* diskcopy = inodebuffer + inodeindex;
  
  mkfs_io_readblock(job, blocknumber, buffer);
  memcpy(inode, diskcopy, sizeof(fsformat_inode_t));
  
  mkfs_freeblockbuffer(job, buffer);
}

void mkfs_writeinode(mkfs_job_t* job, unsigned int inodenumber, fsformat_inode_t* inode) {
  unsigned int blocknumber = MKFS_INODEBLOCK(job, inodenumber);
  unsigned int inodeindex = MKFS_INODEINDEX(job, inodenumber);
  void* buffer = mkfs_allocblockbuffer(job);
  fsformat_inode_t* inodebuffer = (fsformat_inode_t*) buffer;
  fsformat_inode_t* diskcopy = inodebuffer + inodeindex;
  
  mkfs_io_readblock(job, blocknumber, buffer);
  memcpy(diskcopy, inode, sizeof(fsformat_inode_t));
  mkfs_io_writeblock(job, blocknumber, buffer);
  
  mkfs_freeblockbuffer(job, buffer);
}

unsigned int mkfs_allocinode(mkfs_job_t* job, unsigned short inodetype) {
  fsformat_inode_t inode;
  unsigned int inodenumber = job->inode_nextfree;
  job->inode_nextfree++; // The mkfs program just allocates inodes sequentially.
  
  memset(&inode, 0, sizeof(fsformat_inode_t));
  
  inode.type = MKFS_DISKORDER16(inodetype);
  
  // I guess the number of links would generally be 1 for anything created by
  // mkfs.
  inode.linkcount = MKFS_DISKORDER16(1);
  
  // Size is initially set to zero regardless of type.
  // Note that byte order won't matter for zero values but is used by convention
  inode.totalbytes = MKFS_DISKORDER32(0);
  
  mkfs_writeinode(job, inodenumber, &inode);
  
  return inodenumber;
}

#define MKFS_MIN(x,y) \
  (((x) >= (y)) ? (y) : (x))

void mkfs_appenddata(mkfs_job_t* job, unsigned int inodenumber, void* data, int size) {
  unsigned char* buffer = mkfs_allocblockbuffer(job);
  unsigned char* bytedata = (unsigned char*) data;
  fsformat_inode_t inode;
  
  // Load the inode and the offset, these will be updated & saved at the end.
  mkfs_readinode(job, inodenumber, &inode);
  unsigned int offset = MKFS_DISKORDER32(inode.totalbytes);
  
  int countdown = size;
  while (countdown > 0) {
    unsigned int blocktableindex = offset / job->blocksize;
    unsigned int block;
    // TODO: Check blockpart < limit (MAXFILE? check how this is defined)
    if (blocktableindex < NDIRECT) {
      // The block is indexed directly
      block = MKFS_DISKORDER32(inode.addrs[blocktableindex]);
      if (block == 0) {
        // The data block doesn't exist yet, so allocate it.
        block = job->block_nextfree;
        job->block_nextfree++;
        inode.addrs[blocktableindex] = MKFS_DISKORDER32(block);
      }
    } else {
      // The block is NOT indexed directly, so get/create an indirect table.
      // This is stored at the end of the directly-indexed block numbers.
      unsigned int indirectblock;
      
      if (job->fsversion == 0) {
        // Version 0 stores large files as a block-of-block-indexes
        indirectblock = MKFS_DISKORDER32(inode.addrs[job->directblocks]);
        if (indirectblock == 0) {
          // The "indirect" page of pointers is not allocated yet, so allocate it.
          indirectblock = job->block_nextfree;
          job->block_nextfree++;
          inode.addrs[job->directblocks] = MKFS_DISKORDER32(indirectblock);
        }
      } else {
        // Version >= 1 uses an additional layer of indirection, so
        // offsets into large files are indexed by a table-o-tables.
        // This works like the regular system but with an additional
        // layer, with the "tableotables" being stored where the old
        // table would be (and the old being stored in the new table...)
        unsigned int tableotables = MKFS_DISKORDER32(inode.addrs[job->directblocks]);
        if (tableotables == 0) {
          // The "indirect" page of pointers is not allocated yet, so allocate it.
          tableotables = job->block_nextfree;
          job->block_nextfree++;
          inode.addrs[job->directblocks] = MKFS_DISKORDER32(tableotables);
        }
        
        void* ttbuffer = mkfs_allocblockbuffer(job);
        unsigned int* ttids = (unsigned int*) ttbuffer;
        
        mkfs_io_readblock(job, tableotables, ttbuffer);
        indirectblock = MKFS_DISKORDER32(ttids[(blocktableindex - job->directblocks) / (job->blocksize / 4)]);
        
        if (indirectblock == 0) {
          // The "indirect" page of pointers is not allocated yet, so allocate it.
          indirectblock = job->block_nextfree;
          job->block_nextfree++;
          ttids[(blocktableindex - job->directblocks) / (job->blocksize / 4)] = MKFS_DISKORDER32(indirectblock);
          mkfs_io_writeblock(job, tableotables, ttbuffer);
        }
        
        mkfs_freeblockbuffer(job, ttbuffer);
        printf("Used tableotables %d got indirectblock %d\n", tableotables, indirectblock);
      }
      
      void* indirectbuffer = mkfs_allocblockbuffer(job);
      unsigned int* indirectids = (unsigned int*) indirectbuffer;
      
      mkfs_io_readblock(job, indirectblock, indirectbuffer);
      block = MKFS_DISKORDER32(indirectids[(blocktableindex - job->directblocks) % (job->blocksize / 4)]);
      if (block == 0) {
        // The data block doesn't exist yet, so allocate it.
        block = job->block_nextfree;
        job->block_nextfree++;
        // And be sure to store the block index in the indirect table
        indirectids[(blocktableindex - job->directblocks) % (job->blocksize / 4)] = MKFS_DISKORDER32(block);
        mkfs_io_writeblock(job, indirectblock, indirectbuffer);
      }
      // The lookup is now complete so the buffer of indirect pointers is freed:
      mkfs_freeblockbuffer(job, indirectbuffer);
      printf("Final block %d\n", block);
    }
    
    // Find the size of a chunk remaining
    unsigned int chunksize = MKFS_MIN(((blocktableindex + 1) * job->blocksize) - offset, countdown);
    mkfs_io_readblock(job, block, buffer);
    bcopy(bytedata, buffer + offset - (blocktableindex * job->blocksize), chunksize);
    mkfs_io_writeblock(job, block, buffer);
    countdown -= chunksize;
    offset += chunksize;
    bytedata += chunksize;
  }
  
  // Save the inode and offset updated from those loaded at the start.
  inode.totalbytes = MKFS_DISKORDER32(offset);
  mkfs_writeinode(job, inodenumber, &inode);
  
  mkfs_freeblockbuffer(job, buffer);
}

// Creates a new directory entry structure for a given filename+inode combo and
// appends it to the given directory (it's appended as though normal data).
void mkfs_appenddirent(mkfs_job_t* job, unsigned int dirinodenumber, char* name, unsigned int newinodenumber) {
  if (job->fsversion == 0) {
    // Reserve a dirent structure and initialise the entire thing to zero.
    fsformat_dirent_v0_t entry;
    memset(&entry, 0, sizeof(fsformat_dirent_v0_t));
    
    // Configure the fields in the dirent structure.
    entry.inodenumber = MKFS_DISKORDER16(newinodenumber); // TODO: This and some other fields should probably be extended to 32-bit or other/configurable sizes in future versions
    strncpy(entry.filename, name, FSFORMAT_NAMESIZE_OLD);
    
    // And finally append it to the directory as though it's normal file data.
    mkfs_appenddata(job, dirinodenumber, &entry, sizeof(fsformat_dirent_v0_t));
  } else {
    // Reserve a dirent structure and initialise the entire thing to zero.
    fsformat_dirent_v1_t entry;
    memset(&entry, 0, sizeof(fsformat_dirent_v1_t));
    
    // Configure the fields in the dirent structure.
    entry.datainode = MKFS_DISKORDER32(newinodenumber); // TODO: This and some other fields should probably be extended to 32-bit or other/configurable sizes in future versions
    entry.metainode = MKFS_DISKORDER32(0xFFFFFFFF);
    strncpy(entry.filename, name, FSFORMAT_NAMESIZE_NEW);
    
    // And finally append it to the directory as though it's normal file data.
    mkfs_appenddata(job, dirinodenumber, &entry, sizeof(fsformat_dirent_v1_t));
  }
}

// Creates a new file inode and appends it as a directory entry to the given
// directory. Note that the size of a new file begins at zero and data is added
// afterwards with calls to mkfs_appenddata. This function returns the new inode
// number after creating it and adding it to the directory.
// TODO: Add another function to test adding subdirectories, which should
// otherwise work similarly (see mkfs_newfs for code to create the root
// directory, but obviously ".." would be set to parent...)
unsigned int mkfs_newfile(mkfs_job_t* job, unsigned int dirinodenumber, char* name) {
  unsigned int result = mkfs_allocinode(job, T_FILE);
  mkfs_appenddirent(job, dirinodenumber, name, result);
  return result;
}

// Initialises a new filesystem, returning the inode number of the root
// directory. This should perform the work of "mkfs" in a simple mkfs job, then
// afterwards files/dirs can be appended.
unsigned int mkfs_newfs(mkfs_job_t* job) {
  // NOTE: This code assumes that mkfs_allocbuffer returns zeroed memory like
  // the current implementation does.
  unsigned char* buffer = mkfs_allocblockbuffer(job);
  // Write zeroed blocks throughout while the buffer is filled with zeroes.
  for (int blocknumber = 0; blocknumber < job->totalblocks; blocknumber++) {
    mkfs_io_writeblock(job, blocknumber, buffer);
  }
  // The buffer should still be zeroed.
  memcpy(buffer, job->superblock, sizeof(fsformat_superblock_t));
  mkfs_io_writeblock(job, 1, buffer); // Write the superblock at block #1
  
  int result = mkfs_allocinode(job, T_DIR); // This becomes the root directory.
  // TODO: Check that result is ROOTINO and if there's any need to make that configurable
  mkfs_appenddirent(job, result, ".", result);
  mkfs_appenddirent(job, result, "..", result);
  job->rootinodenumber = result; // Store this for consistency so mkfs_finish is guaranteed to use the same value.
  
  return result; // Return the new root inode number.
}

// Finishes the workflow of the "mkfs" program: Finalises the root directory,
// fills the free/used bitmap and closes the output.
void mkfs_finish(mkfs_job_t* job) {
  // Adjust the root directory size to the nearest block boundary (I'm not sure
  // why this needs to be done but I may update comments when I find out...).
  // First load the root directory and get it's size value:
  fsformat_inode_t inode;
  mkfs_readinode(job, job->rootinodenumber, &inode);
  unsigned int rootdirsize = MKFS_DISKORDER32(inode.totalbytes);
  
  // Increment size to block boundary. NOTE: This is a conceptually clear but
  // mechanically expensive way to align to boundaries, it could be replaced
  // if dealing with extra-large blocks.
  while ((rootdirsize % job->blocksize) != 0) {
    rootdirsize++;
  }
  
  // Then set the size value and save the root directory again.
  inode.totalbytes = MKFS_DISKORDER32(rootdirsize);
  mkfs_writeinode(job, job->rootinodenumber, &inode);
  
  // Fill the free/used bitmap up to the number of blocks we've used. NOTE: This
  // assumes we've used blocks contiguously from the start of the disk and not
  // placed a few at the end or any other silly business!
  mkfs_markused(job, job->block_nextfree);
  
  // We're just about done here, time to knock off for smoko break.
  mkfs_io_closedevice(job);
}

int usage(int argc, char** argv, int argerr, const char* error) {
  FILE* o = error ? stderr : stdout;
  char* progname = argv[0];
  fprintf(o, "This program '%s' creates a new filesystem image.\n", progname);
  fprintf(o, "It is designed to support new iterations on simple filesystem design.\n");
  fprintf(o, "It supports a 'version 0' filesystem somewhat-compatible with xv6 (depending on block size etc.),\n");
  fprintf(o, "and a 'version 1' filesystem for in-development versions. A true 'version 2' doesn't exist yet but\n");
  fprintf(o, "will be based on stable iterations of version 1.\n");
  fprintf(o, "USAGE:\n");
  fprintf(o, "  %s -v0|-v1 [--blocksize <nbytes>] --blocks <count> --output <filename> [--allowempty] [--defaulttype <name>] [[--type <typestring>] [--arrayname <name>] [--filename <name>] resource1 [[--type <typestring>] [--arrayname <name>] [--filename <name>] resource2 [...]]]\n\n", progname);
  fprintf(o, "EXAMPLES:\n");
  fprintf(o, "  %s -v0 --output testfs.img --blocksize 1024 --blocks 20000 --allow-empty", progname); 
  return error == NULL ? 0 : -1;
}

#define MAX_RESOURCES 100
FILE* files[MAX_RESOURCES];
char* types[MAX_RESOURCES];
char* filenames[MAX_RESOURCES];
unsigned long sizes[MAX_RESOURCES];

#define BUFFERSIZE 1000
unsigned char buffer[BUFFERSIZE];
  
int main(int argc, char** argv) {
  char* defaulttype = "RESOURCE";
  char* nexttype = NULL;
  char* nextfilename = NULL;
  int nresources = 0;
  int allowempty = 0;
  int skip_underscores = 0;
  
  int version = -1;
  int blocksize = -1;
  int blocks = -1;
  int logblocks = -1;
  int inodes = -1;
  
  char* outputname = NULL;
  
  fprintf(stderr, "SecureLang mkfs for slkern & xv6 filesystems\n");
  
  int argi = 1;
  while (argi < argc) {
    if (!strcmp(argv[argi], "--usage")) {
      usage(argc, argv, argi, NULL);
      return 0;
    } else if (!strcmp(argv[argi], "--type")) {
      if (argi + 1 >= argc) {
        return usage(argc, argv, argi, "Missing argument after --type");
      }
      argi++;
      nexttype = argv[argi];
    } else if (!strcmp(argv[argi], "--filename")) {
      if (argi + 1 >= argc) {
        return usage(argc, argv, argi, "Missing argument after --filename");
      }
      argi++;
      nextfilename = argv[argi];
    } else if (!strcmp(argv[argi], "--output") || (argv[argi][0] == '-' && argv[argi][1] == 'o' && argv[argi][2] == 0)) {
      if (outputname != NULL) {
        usage(argc, argv, argi, "Can't specify output more than once");
        return -1;
      }
      if (argi + 1 >= argc) {
        usage(argc, argv, argi, "Missing argument after --output");
        return -1;
      }
      argi++;
      outputname = argv[argi];
    } else if (argv[argi][0] == '-' && argv[argi][1] == 'o') {
      if (outputname != NULL) {
        usage(argc, argv, argi, "Can't specify output more than once");
        return -1;
      }
      outputname = argv[argi]+2;
    } else if (!strcmp(argv[argi], "--allowempty")) {
      allowempty = 1;
    } else if (!strcmp(argv[argi], "-v0")) {
      if (version != -1) {
        return usage(argc, argv, argi, "Version number has already been set");
      }
      version = 0;
    } else if (!strcmp(argv[argi], "-v1")) {
      if (version != -1) {
        return usage(argc, argv, argi, "Version number has already been set");
      }
      version = 1;
    } else if (!strcmp(argv[argi], "-v2")) {
      return usage(argc, argv, argi, "There is no -v2 format (yet...), this is an early version");
    } else if (!strcmp(argv[argi], "--skip_underscores")) {
      skip_underscores = 1;
    } else if (!strcmp(argv[argi], "--blocksize")) {
      if (argi + 1 >= argc) {
        return usage(argc, argv, argi, "Missing argument after --blocksize");
      } else if (blocksize != -1) {
        return usage(argc, argv, argi, "Block size has already been set");
      } else {
        argi++;
        blocksize = atoi(argv[argi]);
      }
    } else if (!strcmp(argv[argi], "--blocks")) {
      if (argi + 1 >= argc) {
        return usage(argc, argv, argi, "Missing argument after --blocks");
      } else if (blocks != -1) {
        return usage(argc, argv, argi, "Filesystem size has already been set");
      } else {
        argi++;
        blocks = atoi(argv[argi]);
      }
    } else if (!strcmp(argv[argi], "--logblocks")) {
      if (argi + 1 >= argc) {
        return usage(argc, argv, argi, "Missing argument after --logblocks");
      } else if (logblocks != -1) {
        return usage(argc, argv, argi, "Log size has already been set");
      } else {
        argi++;
        blocks = atoi(argv[argi]);
      }
    } else if (!strcmp(argv[argi], "--inodes")) {
      if (argi + 1 >= argc) {
        return usage(argc, argv, argi, "Missing argument after --inodes");
      } else if (inodes != -1) {
      } else {
        argi++;
        blocks = atoi(argv[argi]);
      }
    } else {
      if (nresources + 1 >= MAX_RESOURCES) {
        return usage(argc, argv, argi, "Too many resources");
      }
      files[nresources] = fopen(argv[argi], "rb");
      if (nexttype) {
        types[nresources] = nexttype;
        nexttype = NULL;
      } else {
        types[nresources] = defaulttype;
      }
      if (nextfilename) {
        filenames[nresources] = nextfilename;
        nextfilename = NULL;
      } else {
        char* lastsegment = argv[argi];
        char* s = lastsegment;
        while (*s) { 
          if (*s == '/' || *s == '\\' || *s == ':' || (skip_underscores && *s == '_')) {
            lastsegment = s+1;
          }
          s++;
        }
        filenames[nresources] = lastsegment;
      }
      nresources++;
    }
    argi++;
  }
  
  if (version < 0) {
    return usage(argc, argv, argi, "Expected filesystem version to be defined, e.g. -v0");
  } else if (blocks < 0) {
    return usage(argc, argv, argi, "Expected filesystem size (or number of blocks) to be defined, e.g. --blocks 20000");
  } else if (outputname == NULL) {
    return usage(argc, argv, argi, "Expected output name to be defined, e.g. --output testfs.img");
  } else if (nresources < 1 && !allowempty) {
    return usage(argc, argv, argi, "Expected some resources to add or --allowempty to create an empty filesystem");
  }
  
  // Apply the defaults from the old xv6 filesystem & mkfs code or new defaults
  // if optional settings aren't applied.
  if (blocksize == -1) {
    if (version == 0) {
      fprintf(stderr, "Using default block size of 1024 for xv6 compatibility, but the default may be changed (e.g. 4096) as long as it matches the kernel's BSIZE");
      blocksize = 1024;
    } else {
      blocksize = 4096;
    }
  }
  if (logblocks == -1) {
    logblocks = 30; // 10 possible pages in a filesystem write * 3
  }
  if (inodes == -1) {
    inodes = 200; // 200 files or directories, including special files etc.
  }
  
  printf("Filesystem parameters: block size: %d, number of blocks: %d, log blocks: %d, inodes: %d\n", blocksize, blocks, logblocks, inodes);
  
  // Allocate and initialise the job structure with the appropriate sizings.
  mkfs_job_t* job = mkfs_job_alloc(version, outputname, blocksize, blocks, logblocks, inodes, 12, 1, 2, 14);
  
  // Then create the new filesystem resulting in an inode for the root directory
  int rootdirectory = mkfs_newfs(job);
  
  // Then add the files ("resources") to the filesystem
  for (int resi = 0; resi < nresources; resi++) {
    if (!strcmp(types[resi], defaulttype)) {
      fprintf(stderr, "NOTE: Type name '%s' is ignored by current versions of mkfs but may be used as a hint in the future.\n", types[resi]);
    }
    FILE* f = files[resi];
    unsigned long sz = 0;
    size_t nread;
    
    // Create the file in the new filesyste, returning it's inode.
    int fileinode = mkfs_newfile(job, rootdirectory, filenames[resi]);
    
    // Read from the existing file and append to the file in the new filesystem,
    // this happens in arbitrary blocks based on whatever size is reserved for
    // the buffer (which shouldn't impact the output just the number of cycles).
    while ((nread = fread(buffer, 1, BUFFERSIZE, f)) > 0) {
      /*int nwritten = */ mkfs_appenddata(job, fileinode, buffer, nread);
      //if (nwritten != nread) {
      //  fprintf(stderr, "Error while appending to file '%s' (possibly out of space or beyond per-file size limit etc.)\n", filenames[resi]);
      //  exit(-1);
      //}
      sz += (unsigned long) nread;
    }
    
    fprintf(stderr, "Added %ld bytes in '%s'\n", sz, filenames[resi]);
    sizes[resi] = sz; // Note, this is unnecessary except if you want to print totals etc.
    fclose(f);
  }
  
  // Finalise & save any filesystem information.
  mkfs_finish(job);
  
  exit(0);
}